Make the base by stirring together 125g flour, 4 tablespoons sugar, 1 1/2 teaspoons lemon zest and 1 1/2 teaspoons orange zest. Cut in butter until mixture resembles coarse crumbs; stir in coconut. Mix together egg yolk and water; stir into flour mixture. Form dough into ball.
Press slightly less than half the mixture onto the bottom of a 23cm springform tin with the sides removed. Place on shallow baking tray and bake for 15 minutes or until lightly browned. Let cool. Attach sides onto tin and press remaining mixture all the way up the sides of the tin; set aside.
To make the filling, combine cream cheese, 150g sugar, 3 tablespoons flour, 1 tablespoon lemon zest, 1 tablespoon orange zest, cinnamon and nutmeg. Beat until smooth. Blend in sweet potatoes and eggs. Stir in double cream. Pour mixture into prepared base. Place tin in a shallow baking tray.
Bake in preheated oven for 65 to 70 minutes or until centre of the cheesecake is nearly set.
Cool in tin on wire rack for 15 minutes. Using a small spatula or knife, loosen the edges; cool for an additional 30 minutes. Remove sides of the tin and allow cheesecake to cool completely. Cover and refrigerate for at least 4 hours before serving.